u-boot for Omega2/2+ that fits in existing 192kb partition

[greenbreakfast]

Motivation

Adding Omega2/2+ support to the modern versions of u-boot enables new bootloader features that have been requested by customers.

By ensuring the new u-boot fits in the existing 192kb partition meant for the flash, this new bootloader will be backwards compatible. This means all Omega2 users will be able to benefit, and there will be no added complexity in creating new firmware to support a larger partition or new device variants that ship with the new bootloader

[greenbreakfast]

Progress Log

Working Omega2+ u-boot v2024.04 support

Builds uncompressed u-boot image that is ~500kb. Confirmed working on device but with modified partition table.

Source: https://github.com/OnionIoT/u-boot/tree/v2024.04_add_omega2p

Compressed SPL + u-boot

Extends the above work and builds compressed u-boot-with-spl.bin image that is 190kb ⇒ meets the 192kb size requirement

Encounters an error running on the device:

SPL: Image overlaps SPL

Source: https://github.com/OnionIoT/u-boot/tree/v2024.05_add_omega2p_mod

Debugging Efforts

Source: https://github.com/OnionIoT/u-boot/tree/v2024.05_omega2p_dev
(Extends on work in v2024.05_add_omega2p_mod branch)

Trying to understand Image overlaps SPL error

Modified common/spl/spl_legacy.c to added print statements and enable debug output. Output on device:

U-Boot SPL 2024.04-g97ec1988d4-dirty (Mar 24 2025 - 19:40:05 +0000)
Trying to boot from NOR
SPL: payload image: U-Boot 2024.04-g97ec1988d4-dirty? load addr: 0x9c000000 size: 155285
SPL Validation:
  SPL Start: 0x9c000000
  SPL End:   0x9c009330
  Image Start: 0x9c000000
  Image End:   0x9c025e95
  Image Size:  0x00025e95 (155285 bytes)
  (start >= spl_start && start < spl_end) = 1
  (end > spl_start && end <= spl_end) = 0
  (start < spl_start && end >= spl_end) = 0
  (start > end && end > spl_start) = 0
SPL: Image overlaps SPL

Fix Attempt

Noticed:

1. SPL Start and Image Start are both 0x9c000000
2. Omega2p defconfig defines CONFIG_TEXT_BASE=0x9c000000 (done arbitrarily during initial u-boot work)
3. gardena mt7688 defconfig does not define CONFIG_TEXT_BASE at all

Removed CONFIG_TEXT_BASE=0x9c000000 from omega2p defconfig, rebuilt u-boot-with-spl.bin and tested on device. Output:

U-Boot SPL 2024.04-g97ec1988d4-dirty (Mar 24 2025 - 20:01:25 +0000)
Trying to boot from NOR
SPL: payload image: U-Boot 2024.04-g97ec1988d4-dirty load addr: 0x80200000 size: 155288
SPL Validation:
  SPL Start: 0x9c000000
  SPL End:   0x9c009330
  Image Start: 0x80200000
  Image End:   0x80225e98
  Image Size:  0x00025e98 (155288 bytes)
  (start >= spl_start && start < spl_end) = 0
  (end > spl_start && end <= spl_end) = 0
  (start < spl_start && end >= spl_end) = 0
  (start > end && end > spl_start) = 0
SPL Validation:
  SPL Start: 0x9c000000
  SPL End:   0x9c009330
  Image Start: 0x80200000
  Image End:   0x80200000
  Image Size:  0x00000000 (0 bytes)
  (start >= spl_start && start < spl_end) = 0
  (end > spl_start && end <= spl_end) = 0
  (start < spl_start && end >= spl_end) = 0
  (start > end && end > spl_start) = 0
LZMA: Decompressing 9c009986 to 80200000

And hangs there indefinitely. Assuming that decompressing from higher address (9c009986) to lower address (80200000) won't work. But this brings me to the limit of my understanding of u-boot.